1. Field of the Invention
This invention relates to a method for the separation of a mixed solution of glucose and fructose into liquid glucose and liquid fructose, by using a fixed bed of a strongly acidic cation exchange resin of the alkaline earth metal type, and has it for its object to obtain liquid glucose and liquid fructose of higher purity with a higher yield.
2. Description of the Prior Art
So far, for separating a mixed sugar solution of glucose and fructose into glucose and fructose, it is known to use a cation exchange resin in the calcium form for column chromatographic separation of the mixed solution, as taught by the U.S. Pat. No. 3,044,904, Japanese Patent Publication No. 24807 of 1970 and Austrian Pat. No. 1,083,500. It is also known to separate fructose and glucose from saccharose or a saccharose containing invert sugar, as taught by the Japanese Patent Publication No. 5782 of 1971 and Japanese Provisional Publication No. 101140 of 1976, or to separate fructose and glucose from an isomerized sugar by using a pseudo moving bed, as taught by the Japanese Provisional Publication Nos. 26336 and 88335 of 1978.
These known methods have practically many difficulties and are not useful for industrial application.
The method of the U.S. Pat. No. 3,044,904 teaches a basic principle of separating a mixed solution of fructose and glucose and difficulties are involved in industrial application thereof. The method of the Japanese Patent Publication No. 24807 of 1970 is an improvement over the method of the U.S. Pat. No. 3,044,904, however, it does not lend itself to obtainment of liquid glucose and fructose of high purity with a high yield. In the method of the Japanese Patent Publication No. 5782 of 1971, the starting sugar solution is passed through a cation exchange resin, a part of which is allowed to remain as H type to effect inversion of saccharose contained in the sugar solution and simultaneous adsorption of foreign salts. This known method is again not advantageous for industrial application because an extremely long column is required for elevating the separation efficiency. The method of the Japanese Provisional Patent Publication No. 101140 of 1976 is an improvement over this known method, however, it uses a number of columns and is highly complex in operation and is not practical for industrial application. A pseudo moving bed is used in both the Japanese Provisional Patent Publication No. 26336 of 1978 in which zeolite is used as adsorbing agent and the Japanese Provisional Patent Publication No. 88355 of 1978 in which a cation exchange resin is used as such agent. Both of these methods use a large number of columns and are highly complex in operation and therefore many difficulties are met in industrial application.
Fixed beds are simpler and more reliable than pseudo moving beds in the case of application as industrial devices, however, the method using a fixed bed as taught by the Japanese Patent Publication No. 24807 of 1970 does not lend itself to obtainment of liquid fructose and liquid glucose of higher purity with a high yield, as described above.
In more detail, according to the method of this Patent Publication No. 24807 of 1970, in which a fixed bed of the strongly acidic cation exchange resin of the alkaline earth metal type is used for separating a starting mixed solution of glucose and fructose (hereafter referred to simply as starting solution or liquid) into liquid glucose and liquid fructose, the starting liquid and water are sequentially supplied to the fixed bed so that an artifice of chromatographic separation is employed to effect the desired separation.
Thus, as the starting liquid and water are sequentially supplied to the fixed bed, glucose and fructose are separated chromatographically from each other, and the effluent liquid is separated to some degree into a glucose fraction G and a fructose fraction F, as shown in FIG. 2. This effluent liquid is divided into a dilute glucose solution "a", a glucose solution "b", a mixed solution enriched in glucose "c", a mixed solution enriched in fructose "d", a fructose solution "e", a dilute fructose solution "f" and a dilute solution "g". The dilute solutions "a" and "g" are received in the tanks for dilute solutions and are removed from the system, the glucose solution "b" and the fructose solution "e" are received in their respective tanks and removed as ultimate products from the system, while the mixed solutions "c", "d" and the dilute fructose solution "f" are received in their respective tanks. Then, the mixed solution "c", the starting solution, the mixed solution "d", the dilute fructose solution "f" and water are sequentially supplied to the fixed bed, and the effluent liquid is again received in the respective tanks as shown in FIG. 2. The above procedure is carried out several times for obtaining liquid glucose and liquid fructose.
With this known method, however, adsorption zones for glucose and fructose are located close to each other and hence liquid glucose and liquid fructose cannot be obtained with a high yield.